Preheat your oven to 180°C (350°F).

In a large pot of boiling salted water, cook the pasta shells according to package instructions for around 8–10 minutes until al dente. Drain and toss with olive oil to prevent sticking.

In a medium skillet, add a splash of water and bring it to a simmer. Add the fresh spinach, cooking until wilted, about 2–3 minutes. Drain and squeeze out excess moisture.

In a bowl, combine the mascarpone cheese, wilted spinach, and a generous pour of red pepper sauce. Mix until well-blended and stuff each cooled pasta shell with the mixture.

In a sauté pan, heat two tablespoons of olive oil. Add finely chopped onion and minced garlic, cooking until fragrant. Stir in the herbs and then add the tomato passata and vegetable stock. Let simmer for 10 minutes.

Spread a layer of sauce across the bottom of a baking dish. Arrange the stuffed shells on top and sprinkle generously with mozzarella.

Place the dish in the preheated oven and bake for 15 minutes until the cheese is bubbly and golden. Allow to cool for a few minutes before serving.